Knuckle ring



FIG. 1 is a front elevational view of a knuckle ring showing our new design;

FIG. 2 is a left side elevational view thereof, the right side view being the mirror image of the left side view;

FIG. 3 is a rear end elevational view thereof;

FIG. 4 is a bottom plan view thereof; and,

FIG. 5 is a top plan view thereof. 

The ornamental design for a knuckle ring, as shown and described. 